Miranda Lambert's boyfriend Anderson East calls out Garth Brooks for lip-syncing at the 2017 CMAs

Anderson East is calling out Garth Brooks for lip-syncing at the 2017 CMA Awards on Wednesday night.

East, who dates country superstar Miranda Lambert, took to Instagram on Thursday to reveal that Brooks' decision to lip sync on country music's biggest night -- the same night that Brooks was awarded Entertainer of the Year, no less -- "truly offends" him as a singer-songwriter, People reports.

"I keep a lot of my opinions to myself and respect anyone making music, but as a person who tried to put on the best and most honest show I can night after night... this truly offends me," he wrote. "I was told country music is three chords and the truth."

See photos of Garth Brooks and wife Trisha Yearwood:

The call-out came one day after Brooks performed "Ask Me How I Know" at the 51st Annual CMAs and told People backstage that he opted to lip-sync the performance because of the toll that his exhausting tour schedule has taken on his voice.

"We're in the middle of 12 shows in 10 days," he told People. "Not 10 shows in 12 days, 12 shows in 10 days. We did a game-time call on whether to sing the track or lip sync, and decided to lip sync. The voice just isn't there anymore, and you want to represent country music as best you can."

Fans of the "Friends in Low Places" singer noticed that he was lip-syncing during the show, and when he admitted to the controversial move, they were outraged. Some called the decision "unacceptable" and "not what entertainers of the year do." Anderson East is the most high-profile figure to call Brooks out, though.